The mucus-secreting cells present in the epithelium of alimentary tract mucosae including gastric mucosa are considered to be involved in the maintenance of gastrointestinal functions by synthesis, followed by secretion, of mucus. Gastric mucus in particular is viewed as one of the important defense factors to protect the gastric mucosa from attack by such factors as gastric acid and pepsin.
The mucus production in the human stomach is effected by surface mucous cells (covering epithelial cells) present in the gastric mucosa surface epithelium and gastric gland mucous cells present in the deep part of the gastric gland. Recent years have seen attempts to differentiate individual mucus species produced by these mucous cells. A histochemical staining method has been developed which is specific for the sugar components peculiar to the respective mucus species of surface mucous cells and gland mucous cells, and hence is able to differentiate between them. Thus, the mucus found in the surface mucous cells can be specifically stained by the galactose oxidase-cold thionin Schiff (GOCTS) reaction, while in the gland mucous cells mucus classified as class III by the Concanavalin A paradoxical staining method (Katsuyama, T. and Spicer, S. S. (1978), J. Histochem. Cytochem. 26, 233-250) is found to be specifically localized (Ota, H. et al. (1991), Histochemical J. 23, 22-28). Mucus gel layer covering the surface epithelium of the gastric mucosa has been proved to be a laminar structure of alternating layers of the GOCTS-reactive mucus and the Class III mucus, and the mucus gel layer has been found to contain both mucus species from surface mucous cells and gland mucous cells (Ota, H. et al. (1991), Histochemical J. 23, 22-28).
Katsuyama et al. have elucidated that in normal tissues class III mucus can be found only in the limited glandular epithelia of the alimentary tract ranging from the cardiac glands of the esophagus through the cardiac glands, mucous neck cells and pyloric glands of the stomach, Brunner's glands of the duodenum, the mucous glands of the papilla of Vater and the mucous glands of the pancreatic duct in the head of the pancreas, whereas it can be demonstrated with high incidence in such tumor tissues as in cholecystic adenoma, gallbladder cancer and pancreatic duct cancer (Katsuyama et al. (1989), Byori to Rinsho 7, 1217-1224). Furthermore, Matsuzawa et al. has found, referring to the relationship between metaplasia and cancer, that such forms of tissue as found in the gastric mucosa where strongly GOCTS-positive mucus is found in the surface epithelium of the mucosa and class III mucus is localized in the deep part thereof cannot be seen in normal pancreatic duct tissues but frequently in pancreatic duct tissues with metaplasia or carcinoma (Matsuzawa, K. et al. (1992), Human Pathology 23, 925-933). These study results suggest that data for the diagnosis of cancer diseases or possible cancerization can be presented by determining the gastric type mucus secreted into the body fluid, particularly the gastric gland-type mucus.
As for the specific detection of the human gastric gland-type mucus, no other methods than the above-mentioned Concanavalin A paradoxical staining method have been known to date. The known detection method, however, cannot quantitatively determine the gastric gland-type mucus because of its poor reproducibility of staining and also because of the drawback that the method can be applied only to fixed specimens and hence cannot be applied to the determination of secreted or solubilized mucus.